<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <script>
        let my = 100
        while(true){
            let num = +prompt(`
                请输入你要的传操：
                    1、取款
                    2、存款
                    3、查看余额
                    4、退出
            `)
            if(num===1){
                let qk = +prompt('请输入取款金额')
                if(qk>my){
                    let cun1 = +prompt('当前余额不足，请充值')
                    my= cun1+my
                }else{
                    my= my - qk
                }
            }else if(num===2){
                let cq = +prompt('请输入存款金额')
                my = my+cq
            }else if(num===3){
                alert(`您的余额是${my}元`)
            }else if(num===4){
                document.write(`您的余额：${my}元，欢迎下次光临！！！`)
                break
            }
                
        }
    </script>
</body>
</html>